Circulating ionized and total magnesium in end-stage kidney disease.

BACKGROUND: Circulating magnesium exists in the ionized state and in the undissociated form, either bound to albumin, or complexed to various anions. Until recently, only the measurement of total plasma magnesium has been possible. Now circulating ionized magnesium can be assessed as well. METHODS: Total and ionized plasma magnesium were determined in 43 patients on maintenance hemodialysis (dialysate composition: calcium 1.75 mmol/l, magnesium 0.75 mmol/l) before a dialysis session and in a group of 23 healthy subjects. RESULTS: The total (1.16 [1.03-1.31] versus 0.81 [0.78-0.89] mmol/l; median and interquartile range) and the ionized (0.71 [0.66-0.78] versus 0.54 [0.53-0.59] mmol/l) plasma magnesium levels were significantly higher (p < 0.01) and the ionized plasma magnesium fraction lower (0.61 [0.58-0.65] versus 0.67 [0.64-0.70]; p < 0.02) in patients than in controls. CONCLUSION: The determination of circulating ionized magnesium using selective electrodes is an attractive method to evaluate extracellular magnesium in kidney disease.

Rhabdomyolysis and anesthesia: a report of two cases and review of the literature.

Rhabdomyolysis occurred in two apparently healthy boys aged 9.5 and 5.5 years after general anesthesia with suxamethonium. Mild hyperkalemia and renal failure were observed in the first patient, who was subsequently diagnosed with Becker dystrophy. In the second patient, the clinical presentation was not classic for malignant hyperthermia and a muscle biopsy failed to disclose any pathological finding. A review of the literature revealed 66 pediatric cases (56 boys and 10 girls) of anesthesia-associated rhabdomyolysis. Forty-nine (74%) cases were caused by an underlying, mostly unrecognized congenital muscle disease, and 14 (21%) cases were caused by malignant hyperthermia susceptibility. Hyperkalemia (23 patients), cardiac arrhythmias (38 patients), renal failure (4 patients), and death (11 patients) were the most serious complications of anesthesia-associated rhabdomyolysis. The neuromuscular blocking agent suxamethonium had been used in at least 43 of the patients reported in the literature.